Treatment of cellulosic textile materials to provide fire resistance thereto

ABSTRACT

THE FIRE RESISTANCE OF CELLULOSIC MATERIAL IS IMPROVED BY IMPREGNATING IT WITH A NON-VOLATILE INORGANIC ACID, CYANAMIDE, AND A HALOGENATED ALKYL PHOSPHATE AND THEN HEATING TO EFFECT REACTION BETWEEN THE CELLULOSE AND THE IMPREGNANTS.

United States Patent TREATMENT OF CELLULOSIC TEXTILE MATE- RIALS TOPROVIDE FIRE RESISTANCE THERETO David Blackburn, Shaw, near Oldham, andEdward Haslam, Bolton, England, assignors to Courtaulds Limited,

London, England No Drawing. Filed Aug. 20, 1965, Ser. No. 481,398 Claimspriority, applicatsion Greg: Britain, Aug. 21, 1964,

9 Int. Cl. D06m 13/34 US. Cl. 8116.2 14 Claims ABSTRACT OF THEDISCLOSURE The fire resistance of cellulosic material is improved byimpregnating it with a non-volatile inorganic acid, cyanamide, and ahalogenated alkyl phosphate and then heating to effect reaction betweenthe cellulose and the impregnants.

The invention relates to a process for the treatment of cellulosictextile materials to improve their properties, particularly thefire-resistance.

In US. Pat. No. 2,530,261 a process is described and claimed comprisingimpregnating cellulosic textile fibres, yarns or fabrics with an aqueoussolution containing a non-volatile strong mineral acid and cyanamide andthen drying and making the impregnated material to effect reactionbetween the material, the mineral acid and cyanamide, the reactionconditions being such that the product contains at least 1 percent byweight of combined acid. The acid can be neutralised in part if desiredto an extent not exceeding the formation of the monosubstituted salt.Thus, a typical example of the process would be to use an impregnatingmixture of orthophosphoric acid, ammonium dihydrogen phosphate andcyanamide.

The above process gives valuable improvements in the flame-resistance oftreated fabrics but is not as permanent a treatment as desired.

-We have now devised a modification of the above process givingincreased and durable fire-resistance to treated materials.

According to the present invention a process for the treatment ofcellulosic material comprises impregnating the material with an aqueoussolution of a substantially non-volatile inorganic acid, cyanamide and ahalogenated alkyl phosphate and heating the impregnated material,whereby effecting reaction between the cellulose and the impregnants.

The cellulosic materials which may be treated by the process of thepresent invention may take many forms although the process is mostuseful for the treatment of fabrics and garments. Cellulosic fibrestreated may be in staple fibre or in filament form. The cellulosicmaterial may be of natural or man-made origin; thus, for example,regenerated cellulose made by the viscose, cuprammonium or nitrateprocesses may be treated as may be cotton or linen. The cellulosicmaterials may be treated on their own, as is preferred, or they may betreated when in combination with non-cellulosic materials.

The degree of fire-resistance imparted by the process to treatedmaterials varies according to the conditions used and the nature of thehalogenated alkyl phosphate. As the amount of the impregnants depositedon the material being treated rises, so, within limits, does the degreeI of flame-proofing.

The impregnants may be applied simultaneously, as for example from asingle solution, or they may be applied separately. Preferably they areapplied to the material in a single aqueous solution in a paddingoperation.

The substantially non-volatile inorganic acids which "ice may be used inthe process of the present invention are preferably strong acids,amongst which may be mentioned phosphoric acid, phosphorous acid,pyrophosphoric acid, sulphuric acid and sulphamic acid. The acids may ifdesired be partly neutralised with bases. Mixtures of acids maybeemployed. Any acid used should obviously not be so volatile that itvaporises before it can react with the cellulose in the heatingoperation. Of the acids which may be used, phosphoric acid is preferred.

The amount of acid applied is preferably at least 5 gms. per gms. ofmaterial. Thus if the acid is applied to the material in an aqueoussolution by 2. padding operation to 100 percent pick-up, then thesolution should preferably contain at least 5 percent by weight of theacid. It is prefererd that the amount of the cyanamide applied to thematerial should be at least 10 gms. per 100 gms. of material.

The halogenated alkyl phosphate may take several forms. Thus it may be amono, di-, or tri-esterified phosphate in which some or all of thesubstituent alkyl groups are halogen substituted. It is preferred,largely for reasons of availability and cost, that a chlorinated alkylphosphate should be used. Similarly, the alkyl radical(s) normallycontain not more than four carbon atoms. A mixture of phosphates may beused. We have found a commercial mixture of chlorinated ethyl phosphatescontaining a major proportion of bis-fiwhloroethyl phosphate to besatisfactory. The amount of the halogenated alkyl phosphate applied tothe material should preferably be at least 10 gms. per 100 gms. ofmaterial.

After the material has been impregnated it is heated to effect reactionbetween the cellulose and the impregnants. The temperature of heatingused should preferably be high enough to cause the reaction to proceedat a suitable rate Without being so high as to cause degradation orevaporation of the cellulose or impregnants respectively. A temperaturein the range of from 100 C. to 150 C. may generally be usedsatisfactorily.

When cyanamide is heated, some of the dimer dicyanodiamide(cyanoguanidine) is formed. As a modification of the process of theinvention, the cyanamide may be replaced 'wholly or partly by the dimer.

Materials treated by the present process may also be treated withconventional finishing agents as and if desired before or after theimpregnation and baking steps. It is also possible to use someadditional compounds, for example formaldehyde, in the impregnation ofthe cellulosic material before heating. Some use of formaldehyde orother cross-linking agents improves the crease-resistance of the treatedmaterials.

The process of the invention is illustrated by the following examples.The mixed chloroethyl phosphates used therein being a commerciallyavailable mixture consisting of about 53 percent by weight ofbis-fi-chloroethyl phosphate, about 35 percent by weight ofmono-B-chloroethyl phosphate and about 12 percent by weight oforthophosphoric acid.

EXAMPLE 1 A woven fabric weighing about 5 ozs. per square yard andconsisting wholly of viscose rayon staple fibres was padded to 100percent wet pick-up with an aqueous solution containing:

- Percent w./w. Phosphoric acid 15 Cyanamide 20 Mixed chloroethylphosphates 15 The padding solution was prepared immediately before thepadding was performed by mixing an aqueous solution containing thephosphoric acid and the chlorinated ethyl phosphates with an aqueoussolution of the cyanamide. After padding the fabric was dried and bakedat C. for 5 minutes.

The resultant treated fabric was found to contain 3.2 percent by weightof phosphorus and 2.5 percent by weight of nitrogen. When submitted tothe Vertical Bunsen Test, as described in British Standard No. 3119'(method of test for flame-proof materials), the fabric charred but didnot ignite and exhibited no afterglow.

A sample of the treated fabric was washed in a solution containing gms.per litre of soap and 2 gms. per litre of soda ash for 5 minutes at 40C. then dried. After a total of 5 successive washes the fabric was againtested for fire-resistance and found only to char, any slight ignitionbeing extinguished on removal of the flame.

After a further five Washes as above the fabric could be made to burnvery slowly in the Vertical Bunsen Test to leave a strong charred fabricskeleton. The fabric was, however, self-extinguishing on removal of theigniting flame.

EXAMPLE 2 EXAMPLE 3 A sample of the same fabric as used in Example 1 waspadded to 100 percent pick-up through a solution containing:

Percent w./w.

Pyrophosphoric acid Mixed chloroethyl phosphates 15 Cyanamide and wassubsequently dried at 60 baked for 5 minutes at' 105 C., and then rinsedin hot water.

When tested according to British Standard No. 3119 before and after 5 ofthe washes, as described in Example 1, the fabric extinguishedimmediately after removal of the igniting flame and exhibited noafterglow.

EXAMPLE 4 The procedure of Example 3 was followed with one exception,namely the pyrophosphoric acid was replaced by sulphuric acid. Whentested prior to washing, the fabric extinguished immediately afterremoval of the igniting flame and exhibited no afterglow. When testedafter five washes (as in Example 1) the fabric still extinguished onremoval of the flame, but there was some afterglow in the charred regionwhich ceased within ten seconds.

EXAMPLE '5 A sample of the same fabric as used in Example 1 was paddedto 100 percent pick-up through a solution containing:

Percent w./w.

Phosphoric acid 15 Mixed chloroethyl phosphates 15 Cyanamide 10Dicyanodiamide 8 Subsequently, the fabric was dried at 60 C., baked forminutes at 105 C., and then rinsed in hot water. When tested before andafter two of the washes (as in Example 1), the fabric extinguished onremoval of the flame and exhibited no afterglow.

EXAMPLE 6 A fabric weighing about 20 ozs. per square yard of the typenormally used for the manufacture of electric blan- 4 kets andconsisting of a Sarille (registered trademark) regenerated celluloseyarn weft and a cotton warp was padded to 100 percent pick-up through asolution containing:

Percent w./w.

Phosphoric acid 7.5 Mixed chloroethyl phosphates 7.5 Cyanamide 15 Thefabric was subsequently dried at 60 C., baked for 5 minutes at 105 C.,and then rinsed in hot water.

The resultant fabric was found to meet the requirements of BritishStandard No. 3121 (Performance Requirements of Materials Described As ofLow Flammability). This involves testing the fabric according to BritishStandard No. 2693 (Tests for the Flammability of Fabrics) after washingthe fabric twelve times for 30 minutes at C. to C. in a specifieddetergent. Both before and after these washes the treated fabric camewithin the flame not propagated classification and there was noafterglow.

EXAMPLE 7 A pile fabric weighing about 10 ozs. per square yard andconsisting of a cotton backing fabric and a continuous filament viscoserayon pile, the proportions by weight of cotton and rayon being aboutequal, was padded to percent pick-up through a solution containing:

Percent w./ W.

Phosphoric acid 15 Mixed chloroethyl phosphates 2 15 Cyanamide 20 andwas subsequently dried at 60 C., baked for 5 minutes at C., and thenrinsed in hot water.

When tested according to British Standard No. 2963 after 6 of the washesspecified in British Standard No. 3121, the fabric was classified asflame not propagated and there was no afterglow.

EXAMPLE 8 A woven fabric weighing about 3.6 ozs. per square yard andconsisting of Vincel (registered trademark) regenerated cellulose staplefibres, was padded to 100' percent pick-up through a solutioncontaining:

Percent w./w.

Phosphoric acid 15 Mixed chloroethyl phosphates 15 Cyanamide 20 and wassubsequently dried at 60 C., baked for 5 minutes at 105 C., and thenrinsed in hot water.

When tested according to British Standard No. 3119 after 3 of the washesspecified in British Standard No. 3121, the flame extinguishedimmediately on removal of the igniting flame and exhibited no afterglow.

What we claim is:

1. A process for improving the fire-resistance of cellulosic materialcomprising impregnating the material with an aqueous solution of asubstantially non-volatile inorganic acid, cyanamide and a halogenatedalkyl phosphate and heating the impregnated material, thereby effectingreaction between the cellulose and the impregnants.

2. A process according to claim 1, wherein a mixture of non-volatileinorganic acids is used in the impregnating solution.

3. A process according to claim 1 wherein the acid in the impregnatingsolution is in part neutralised by a base to give a water-soluble salt.

4. A process according to claim 1 wherein the acid is phosphoric acid,phosphorous acid, pyrophosphoric acid, sulphuric acid or sulphamic acid.

5. A process according to claim 1 wherein the cyanamide is replaced atleast in part by dicyanodiamide.

6. A process according to claim 1, wherein the alkyl radical in thehalogenated alkyl phosphate contains not more than four carbon atoms.

7. A process according to claim 6 wherein the halogenated alkylphosphate is a chlorinated alkyl phosphate.

8. A process for improving the fire-resistance of cellulosic materialcomprising impregnating the material with at least gms. of asubstantially non-volatile inorganic acid, at least gms. of cyanamideand at least 10 gms. of a halogenated alkyl phosphate per 100 gms. ofmaterial from an aqueous solution of the inorganic acid, cyanamide andthe halogenated alkyl phosphate and heating the impregnated material,thereby eflecting reaction between the cellulose and the impregnants.

9. A process according to claim 8 'wherein the acid is phosphoric acid,phosphorous acid, pyrophosphoric acid, sulphuric acid or sulphamic acid.

10. A process according to claim 8 wherein the alkyl radical of thehalogenated alkyl phosphate contains not more than four carbon atoms.

11. A process according to claim 10 wherein the halogenated alkylphosphate is a chlorinated alkyl phosphate.

12. A process according to claim 8 wherein the impregnated material isheated to a temperature within the range of from 100 C. to 150 C.

13. A process for improving the fire-resistance of cellulosic materialcomprising impregnating the material with at least 5 gms. of phosphoricacid, phosphorous acid, pyrophosphoric acid, sulphuric acid or sulphamicacid, at least 10 gms. of cyanamide and at least 10 gms. of ahalogenated alkyl phosphate, wherein the alkyl radical contains not morethan four carbon atoms, per 100 gms. of material from an aqueoussolution containing the inorganic acid, cyanamide and the halogenatedalkyl phos- 6 phate, and heating the impregnated material to atemperature within the range of from C. to 150 C., thereby efiectingreaction between the cellulose and the impregnants.

14. A process for improving the fire-resistance of cellulosic materialcomprising impregnating the material with at least 5 gms. of phosphoricacid, at least 10 gms. of cyanamide and at least 10 gms. of achlorinated alkyl phosphate, wherein the alkyl radical contains not morethan four carbon atoms, per 100 gms. of material from an aqueoussolution containing the phosphoric acid, cyanamide and the chlorinatedalkyl phosphate and heating the impregnated material to a temperaturewithin the range of from 100 C. to 150 C., thereby effecting reactionbetween the cellulose and the impregnants.

References Cited UNITED STATES PATENTS 2,530,261 11/1950 Morton et a18-116.2 2,714,100 7/1955 Toy et al 8116P 2,743,232 4/1956 Chance et al.8-l20P 2,979,374 4/1961 Drake et a1 8l2OP 2,991,146 7/1961 Babiarz eta1. 8-120P GEORGE F. LESMES, Primary Examiner J. P. BRAMMER, AssistantExaminer US. Cl. X.R. 8-1163,

